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First, I assume you are either putting the AVCHD files directly into the burning module, or else doing your editing then jumping straight to Share > Create Disc > DVD. This will open the project file (VSP) in the burning timeline. Either way, even though you have a powerful computer, you are asking it to perform two complex tasks in the one burning operation: first it has to convert the AVCHD/AVCHD VSP into DVD-compatible mpeg-2; and then it has to burn that new video to DVD.Though this should be possible, it causes some problems for some users.
We recommend that after you do your editing, you go instead to Share > Create Video File > DVD to first prepare the new DVD-compatible mpeg-2 in the editing module. When it is done, then you can go to Share > Create Disc > DVD, where you insert the new mpeg-2 in the burning timeline, and proceed from there.
Try that, and see if it makes a difference. You won't be losing any time as it will still take the same amount of time to convert the AVCHD, whether it is done in the editing or the burning modules. But by making the burning process less complicated, you may have a better chance of success.
If your project is longer than one hour, then you would select Share > Create Video File > Custom. You would then need to lower the bitrate so as to be able to fit the resulting file on a DVD. As a rule of thumb, the default 8000 kbps will allow one hour to be burned to a 4.3 GB single layer DVD. A bitrate of 6000 kbps will allow 90 minutes; and 4000 kbps will allow 2 hours. Note that as you lower the bitrate, you also lower the quality of the final DVD. 6000 will still give you very good quality, but 4000 will only be about the same as VHS tape.
